The stability of table salt, double fortified with various formulations of iodine and microencapsulated iron, has been investigated under actual field conditions of storage and distribution in the coastal and highland regions of Kenya. Twenty-nine 200 g sample packets of double fortified salt in sealed polyethylene bags and a datalogger for monitoring temperature and humidity were packaged into a typical bundle which was inserted into the distribution network starting from a salt manufacturer's facility to the consumer. High iodine retention values were obtained during the three-month study. Most of the iron was retained with less than 20% of the ferrous iron oxidized to ferric iron, and about 25% of the iron in formulations with sodium ferric EDTA (NaFeEDTA) reduced to ferrous iron. Double fortified salt with ferrous fumarate was more stable than those prepared with the other iron premixes. The polyethylene film overwrap of salt packs in the bundles provided significant protection from ambient humidity. Salt double fortified with iodine and microencapsulated iron ferrous fumarate premix was generally quite stable because both iodine and the ferrous iron were protected during the three months in the distribution and retail network in typical tropical conditions in Kenya's highlands and humid lowlands. (c) 2005 Elsevier Ltd. All rights reserved.